The CASPASE-8 Drug Discovery Kit is a complete assay system designed to screen caspase-8 inhibitors. It contains both a colorimetric substrate (IETD-pNA) and a fluorogenic substrate (IETD-AMC). Cleavage of the p-nitroanilide (pNA) from the colorimetric substrate increases absorption at 405nm. The fluorescent assay is based on the cleavage of 7-amino-4-methylcoumarin (AMC) dye from the C-terminus of the peptide substrate. Cleavage of the dye from the substrate increases its fluorescence intensity at 460 nm. The assays are performed in a convenient, 96-well microtiter-plate format. The kit is useful to screen inhibitors of caspase-8, a potential therapeutic target. An inhibitor, IETD-CHO (aldehyde), is included for use as a control.